This invention relates to surgical stapler apparatus, and more particularly to surgical stapler apparatus having a longitudinally flexible shaft intermediate the portion of the apparatus which performs the stapling function and the actuator portion of the apparatus. (For simplicity, discussion hereinafter will largely be confined, in terms, to surgical staplers, but it is to be understood that the scope of the invention includes apparatus for applying any type of surgical fasteners.)
There are several known types of surgical staplers in which the stapling function takes place at a location which is relatively remote from the location at which the stapler is held and actuated by the operator. Examples of such staplers are the linear closure surgical staplers shown in U.S. Pat. No. 3,494,533, issued Feb. 10, 1970, to Green et al., and commonly assigned herewith, and the circular anastomosis surgical staplers shown in U.S. Pat. No. 4,304,236, issued Dec. 8, 1981, to Conta et al., and commonly assigned herewith. Typically, in instruments of the types exemplified by these patents, tissue to be stapled is clamped between an anvil assembly and a staple holding assembly, both of which are located at the distal end of the instrument. The clamped tissue is stapled by driving one or more staples from the staple holding assembly so that the ends of the staples pass through the tissue and are clinched by contact with the anvil assembly. The forces required to operate the instrument are applied by the operator of the instrument to one or more actuator elements located at or near the proximal end of the instrument. The distal and proximal portions of the instrument are joined by a longitudinal connecting shaft structure along which the actuating forces and motions are transmitted to the distal operating elements. This type of construction, including relatively widely spaced distal and proximal portions, may be employed for any of several reasons, such as the relative inaccessibility of the tissue to be stapled, or the need to see the tissue well during stapling.
In some applications of instruments of the types mentioned above, it may be desirable for the longitudinal shaft structure joining the distal and proximal portions of the apparatus to have at least a section which can be bent in a direction transverse to the longitudinal axis of the instrument (i.e., which is longitudinally flexible). This may facilitate placement of the instrument in particular body structures, it may facilitate reaching remote or relatively inaccessible stapling sites, or it may allow the staples to be positioned at the stapling site at various angles relative to the operator of the instrument.
The approach taken in the present invention is to transmit only a small force hydraulically along the flexible shaft and to use that force to generate or trigger a larger force in the applicator to apply the staples to the tissue. By localizing the large stapling force in one end of the apparatus, and making the force transmitted along the flexible shaft sufficiently small, the flexible shaft can be kept from straighting significantly during application of the staples.